Poster Number 105
See more from this Division: General Discipline Sessions
See more from this Session: Precambrian Geology (Posters)
Abstract:
Leucosomes in sillimanite-bearing gneisses are granitic in composition and their mineral assemblages suggest that they formed by muscovite and biotite consuming dehydration melting of the surrounding gneisses. The oldest generation of leucosomes (G1) is folded by F1 and forms centimetric-scale parasitic folds whose sense of shear reverses across the F1 limbs suggesting that G1 is syn-deformational to F1. A younger generation of coarse grained granitic leucosomes (G2) crosscuts F1 parasitic folds, postdating the first shortening event. Leucosomes in mafic gneisses are tonalitic (T1, T2) in composition and formed dehydration melting reactions in the mafic gneisss that locally produced large orthopyroxene crystals. T1 leucosomes are parallel to the S1 gneissic banding while T2 leucosomes occur in shears that cut this banding. The relationship between leucosomes and F1 structures should make it possible to use zircons in the leucosomes to date both migmatization and the F1 deformational event.
See more from this Division: General Discipline Sessions
See more from this Session: Precambrian Geology (Posters)